PROJECTSUMMARY Therearenopharmacotherapiesforstimulantabuse,includingmethamphetamine(METH)andrelapserates arehigh.Relapsetriggeredbyremindersofdruguseisaparticularchallengetoprevent,astheunderlying memoriesexertapowerfulmotivationalinfluenceoverbehaviorandrepresentalifelongrelapseriskfactor. Learningissupportedbystructuralplasticityindendriticspines,drivenbytraining-inducedactinpolymer- ization.Memorystabilityissubsequentlyachievedbyarrestingactindynamics,stabilizingthecytoskeleton.As aresult,memoryisimpervioustoactindepolymerizationwithinminutesoflearning.However,priorworkinthe labdiscoveredthattheactincytoskeletonsupportingMETHmemoriesremainsuniquelydynamicinthe amygdalalongaftertraining.Thisenablesselective,retrieval-independentdisruptionofMETH-associated memoriesanddrugseekingwithasingleadministrationofanactindepolymerizer.Becauseactin?scritical rolesinthebodylimititstherapeuticpotential,focusshiftedtononmusclemyosinII(NMII),adirectdriverof learning-stimulatedactinpolymerizationinspines.TheeffectofNMIIinhibitionisspecifictotheamygdalaand METH.Indeed,NMIIinhibitionhasnoeffectonMETHmemorieswhenotherregionsofthedrug-memory neuralcircuitaretargetedandthereisnosimilarretrieval-independenteffectonmemoriesforfear,food rewardorotherdrugsofabuse,includingopioids.GeneticandpharmacologictargetingofNMIIestablishedit isaviabletherapeutictargetandanNIH-fundedmedicationdevelopmentprojectforaclinicallysafeNMII inhibitorisunderway(UH3NS096833).However,fundamentalknowledgeneededtounderstandandfurther leveragethisspecificityislacking.Thiswillbeaddressedthroughthecentralhypothesisinthisnewproject: thatMETH-associatedmemoriesareuniquelysupportedintheamygdalabyNMII,leavingthosememories selectivelyvulnerabletodisruptionlongafterlearning,evenwhenotherassociativelearningisintroduced.The focusofthisapplicationistwo-fold:(1)Thekeymechanisticquestionregardingthespecificrequirementof theamgydala,actin-NMIIandMETHforselectivememorystoragedisruptionwillbeaddressed.Forthis,the impactofMETH-relatedneuromodulators(Aim1),aswellasNMIIphosphorylationandinteractingpartners (Aim2)willbestudiedonNMII-dependentBLAsynapticactindynamicsandMETH-associatedmemory,witha focusonfactorsthatareuniquetoMETHandtheBLA.Onceidentified,themechanism(s)responsiblecould beharnessedtorenderrelapse-inducingmemoriesforotherdrugsofabusevulnerabletodisruption.(2) BecausemostindividualswithMETHusedisorderusemultiplesubstances,includingopioids,itisnecessary todeterminetheimpactofpolydrugadministrationonMETHmemorysusceptibilitytoNMIIinhibition. PreliminarydataindicatethatMETHconferssusceptibilitytopreviouslyimperviousopioidassociations. Technicallyinnovativeapproacheswillbeemployedthroughouttheproject,spanningfromsinglesynapse manipulationsinlivetissueslicestomemory-basedself-administrationstudies.